Camshaft adjuster

ABSTRACT

Camshaft adjuster for an internal combustion engine with a cylinder head, with a drive element and a driven element, the drive element and the driven element can be rotated relative to each other about a common axis, the drive element and the driven element form work chambers acting opposite each other, the work chambers are pressurizable with hydraulic medium, in order to achieve a relative rotation between the drive element and the driven element, and a control valve is arranged in the driven element, the control valve has a valve housing and a control piston that is arranged in the valve housing and is used for controlling the hydraulic medium, the control valve is arranged coaxial to the common axis, and a one-piece radial bearing point constructed by the driven element is provided for support on the cylinder head outside of the axial area of the work chambers.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No.: 102012202823.4, filed Feb. 24, 2012.

FIELD OF THE INVENTION

The invention relates to a camshaft adjuster.

BACKGROUND

Camshaft adjusters are used in internal combustion engines for varying the control times of the combustion chamber valves, in order to be able to variably shape the phase relation between a crankshaft and a camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. The adaptation of the control times to the current load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated in a drive train by means of which a torque is transferred from the crankshaft to the camshaft. This drive train can be constructed, for example, as a belt drive, chain drive, or gearwheel drive.

In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of pressure chambers that act against each other and can be pressurized with hydraulic medium. The drive element and the driven element are arranged coaxially. By filling and emptying individual pressure chambers, a relative movement is generated between the drive element and the driven element.

One possible type of hydraulic camshaft adjuster is the vane cell adjuster. The vane cell adjuster has a drive element formed as a stator, a driven element formed as a rotor, and a drive wheel with external teeth. The driven element is usually formed so that it can be locked in rotation with the camshaft. The drive element contains the stator and the drive wheel. The drive element and the drive wheel are locked in rotation with each other or are alternatively constructed as a single piece. The driven element is arranged coaxial to the drive element and within the drive element. The driven element and the drive element form oil chambers that act in opposite directions with their vanes extending in the radial direction and these chambers can be pressurized by oil pressure and allow a relative rotation between the drive element and the driven element. The vanes are constructed either integrally with the driven element or the drive element or are arranged as “inserted vanes” in grooves of the driven element or drive element provided for this purpose. The vane cell adjusters further have various sealing covers. The drive element and the sealing covers are secured with each other by several screw connections.

Another type of hydraulic camshaft adjuster is the axial piston adjuster. Here, a displacement element that generates a relative rotation between a drive element and a driven element using helical gearing is shifted in the axial direction by oil pressure.

DE 10 2004 026 863 A1 discloses a camshaft adjuster with a drive element and a driven element. The camshaft is connected to the driven element by means of a non-positive, positive, or material fit connection.

In DE 10 2008 050 134, a camshaft adjuster is described in which a connection element is provided in the driven part. The connection element is fixed in the driven part by means of a positive-fit connection. The connection element is further attached to a camshaft. The connection element has recesses that are used for the oil supply. The oil supply is controlled by means of a hydraulic valve that is provided in the connection element.

A camshaft adjuster with a drive element and a driven element is disclosed in DE 103 34 690 B4. A peg is formed integrally from the driven element. The peg is used for connecting to the camshaft. Several oil supply channels are further arranged in the driven element.

DE 10 2009 052 841 A1 discloses a camshaft adjuster in which a camshaft insert is used for attaching the rotor to the camshaft. The camshaft insert is locked in rotation with the rotor by means of a nut. A longitudinal bore that holds a central valve is provided in the camshaft insert.

In U.S. Pat. No. 6,871,621 B2, a camshaft adjuster is described in which the rotor is screwed to the camshaft by means of a screw. The central valve is inserted from one end of the driven element and screwed to this driven element.

SUMMARY

The objective of the present invention is to provide a camshaft adjuster that can be produced economically.

This is achieved according to the invention by a camshaft adjuster for an internal combustion engine with a cylinder head, with a drive element and a driven element, wherein the drive element and the driven element can be rotated relative to each other about a common axis and wherein the drive element and the driven element form work chambers acting opposite each other, wherein the work chambers can be pressurized with hydraulic medium, in order to achieve a relative rotation between the drive element and the driven element, and wherein a control valve is arranged in the driven element, wherein the control valve has a valve housing and a control piston that is arranged in the valve housing and is used for controlling the hydraulic medium, and wherein the control valve is arranged coaxial to the common axis, wherein a one-piece radial bearing point constructed by the driven element is provided for support on the cylinder head outside of the axial area of the work chambers.

Through the integration of the radial bearing point on the driven element, a compact structural unit is achieved that allows the camshaft adjuster to be inserted as a structural unit into a bearing frame of an open cylinder head. Furthermore, a true-running error can be minimized by the one-piece construction.

In one advantageous construction, the control valve is fixed in the axial direction in the driven element by a non-positive fit connection. In a non-positive fit connection, the parts are held in their mutual position by an external force, for example, a friction force. The non-positive fit connection can be, for example, a ring that is joined to the driven element by a longitudinal or transverse interference fit.

In one preferred construction, the control valve is fixed in the axial direction in the driven element by a positive fit connection. In a positive-fit connection, the force is transmitted through the shape of the parts involved in the connection. For this purpose, a positive-fit connection must be produced between two active contacting surfaces. The positive-fit connection can be, for example, a retaining ring or an expansion ring.

In one construction of the invention, the driven element has an anti-rotation device for the control valve, so that an installation position defined in the peripheral direction is specified. The anti-rotation device is required so that the control valve and the driven element cannot rotate relative to each other when the camshaft adjuster is activated. The anti-rotation device can be, for example, an axial groove, notch, recess, or the like in the driven element. The anti-rotation device in the driven part is advantageously produced by pressing, sintering, or calibrating methods, wherein the high costs due to milling can be avoided.

The control valve engages in the anti-rotation device of the driven element. To allow this, projecting flaps, tabs, or other raised section are provided on the control valve.

In one construction of the invention, the valve housing is formed integrally with the driven element, wherein the driven element forms a guide surface for guiding the control piston of the control valve. The valve housing can be formed, for example, by a bore in the driven element, wherein the bore forming the valve housing is here arranged coaxial to the axis about which the drive element and the driven element can rotate relative to each other. The bore can be constructed as a through hole or as a blind hole. The other components of the control valve, such as the control piston and a compression spring, can be inserted as “insert pieces” into this bore.

By integrating the valve housing in the driven element, the control piston is consequently guided by the driven element. In the axial direction, the control piston can move in the driven element and thus can be positioned in any axial position relative to the driven element. This has the advantage that the material and production costs that occur for a control valve with a separate valve housing can be reduced, just like the assembly costs. Another advantage of the invention is that the control piston can be used without tension and deformation in the driven element.

In a preferred construction, the hydraulic medium can be fed into the control valve by hydraulic medium channels formed in the camshaft. Alternatively, a supply of the hydraulic medium into the control valve can be provided in the axial or radial direction in the radial bearing position. For the supply and distribution of the hydraulic medium, hydraulic medium channels are provided in the camshaft or also in the radial bearing position according to the embodiment. In addition, the driven element has other hydraulic medium channels that interact with openings of the control valve. These hydraulic medium channels can run in the driven element in the radial or also in the axial direction to the work chambers and through openings, such as bores or through recesses, such as channels, grooves, or other formations. Through the axial positioning of the control piston, the different openings of the control valve and the hydraulic medium channels are connected to each other hydraulically or separated from each other.

In another construction of the invention, the driven element has a radial projecting peg for attachment to a camshaft. The peg can be made, for example, from a solid material or like a kind of sleeve or pipe. By the use of a positive-fit, non-positive fit, or material fit connection, the peg can be locked in rotation with the camshaft. According to the kind of connection, the lateral surface of the peg can be adapted accordingly. Here, the lateral surface of the peg can be smooth, roughened, or provided with raised sections.

In one construction of the invention, the peg is formed integrally with the driven element. The peg can be locked in rotation with the driven element by a material fit, positive fit, or non-positive fit connection. Alternatively, it is also possible to form the peg as a separate component or as multiple components. In this way it is possible that the peg is formed from multiple pins.

In one advantageous construction, the driven element has an axial bearing and a part of the axial bearing is formed integrally with the driven element. Optionally, the axial bearing could also be formed separately and connected to the driven element by a non-positive fit, positive fit, or material fit connection. The other part of the axial bearing can be formed by the camshaft or the cylinder head.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described below with reference to three figures. Shown are:

FIG. 1 a section view through the camshaft adjuster according to the invention,

FIG. 2 a section view through a driven element of the camshaft adjuster according to the invention, and

FIG. 3 a side view of the camshaft adjuster according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a camshaft adjuster 1 with a camshaft 2 that is shown partially and is formed with a tubular shape. The camshaft adjuster 1 has a drive element 3 that is formed as a stator 4 and a driven element 5 that is formed as a rotor 6. The stator 4 and the rotor 6 can be rotated about a common axis la relative to each other. Furthermore, a drive wheel 4 a is formed integrally on the stator 4. In addition, the camshaft adjuster 1 has a cover 7 on which a spring 8 is suspended. The cover 7 is connected to the stator 4 by a screw connection 9.

As can be further seen, the camshaft adjuster 1 has a first axial bearing point 10 and a second axial bearing point 11 that are formed with a ring shape. The first axial bearing point 10 is connected to a section of the rotor. The second axial bearing point 11 is provided on the camshaft end 2 a facing the rotor 6.

For better understanding of the structure of rotor 6, in addition to FIG. 1, FIG. 2 is also referenced. As can be seen from FIG. 2, the rotor 6 has a step-shaped structure that forms three rotor areas 6 a, 6 b, 6 c.

A first rotor area 6 a has vanes 12. The vanes 12 are formed integrally on the rotor 6. With the stator 4, the vanes 12 of the rotor 6 form work chambers (not shown) that can be pressurized with hydraulic medium.

On the rotor area 6 a on which the vanes 10 are formed integrally, a second rotor area 6 b connects that forms a radial bearing point 13. The radial bearing point 13 is formed integrally on the rotor 6. As FIG. 2 shows, the radial bearing point is smaller in diameter than the rotor area 6 a that has the vanes 10. The radial bearing point 11 is provided for the support of a cylinder head.

On the rotor area 6 b, a third rotor area 6 c connects that is formed by a peg 14. The peg 14 is formed from a solid material and is smaller in diameter than the rotor area 6 b that forms the radial bearing point 11. The peg 14 is used for the rotationally locked attachment to the camshaft 2. For this purpose, the peg 14 is joined by a non-positive fit connection into the open camshaft end 2 a.

The rotor 6 has a blind bore 15 coaxial to the axis 1. The blind bore 15 extends in the axial direction along the first rotor area 6 a and the second rotor area 6 b. As can be seen, several bores 16 are provided in the blind bore 15. The bores 16 form hydraulic medium channels 17. The hydraulic medium channels 17 extend in the radial direction and are used to provide the not-shown work chambers with hydraulic medium. In the area of the bores 16 there are additional ring channels 18 that guide the hydraulic medium into the hydraulic medium channels 17.

As can be further seen from FIG. 2, the rotor 6 has, in the area of the peg 12, the bore 19. In the embodiment, two such bores 19 are provided. The bores 19 run in the radial direction and are formed as passage bores. The bores 19 are used in the rotor as supply 20. This supply 20 is connected to a not-shown compressed medium pump. The hydraulic medium is led in the direction of a control valve 21 a by the supply 22.

Furthermore, the blind bore 15 forms a valve housing 21 of the control valve 21 a. In the valve housing 21 integrated in the rotor 6, a control piston 21 b, a not-shown compression spring of the control valve 21 a are inserted as insert parts. The valve housing 20 formed by the blind bore 15 forms a guide surface for the not-shown control piston. The control piston 21 b can move in the axial direction into the blind bore 15 and interacts with the hydraulic medium channels 17 in the rotor 6.

The rotor 6 has an anti-rotation device 22 for the control valve. The anti-rotation device 22 is formed as an axial groove 23 in the rotor 6 in which the control valve 21 a can engage.

The securing of the control valve 21 a in the axial direction can be seen from FIG. 3. The axial securing of the control valve 21 a is realized with a positive-fit connection by a retaining ring 24.

LIST OF REFERENCE NUMBERS

1 a Axis

1 Camshaft adjuster

2 Camshaft

2 a Camshaft end

3 Drive element

4 Stator

4 a Drive wheel

5 Driven element

6 Rotor

6 a First rotor area

6 b Second rotor area

6 c Third rotor area

7 Cover

8 Spring

9 Screw connection

10 First axial bearing point

11 Second axial bearing point

12 Vane

13 Radial bearing point

14 Peg

15 Blind hole

16 Bore

17 Hydraulic medium channels

18 Ring-shaped channel

19 Bore

20 Feed

21 Valve housing

21 a Control valve

21 b Control piston

22 Anti-rotation device

23 Axial groove

24 Retaining ring 

1. A camshaft adjuster for an internal combustion engine with a cylinder head, the camshaft adjuster comprising: a drive element and a driven element, the drive element and the driven element are rotatable relative to each other about a common axis, the drive element and the driven element form work chambers acting opposite each other, the work chambers are pressurizable with hydraulic medium, in order to achieve a relative rotation between the drive element and the driven element, and a control valve is arranged in the driven element, the control valve has a valve housing and a control piston that is arranged in the valve housing and is used for controlling the hydraulic medium, the control valve is arranged coaxial to the common axis, and a one-piece radial bearing point constructed by the driven element is provided for support on the cylinder head outside of an axial area of the work chambers.
 2. The camshaft adjuster according to claim 1, wherein the control valve is fixed in the axial direction by a positive-fit in the driven element.
 3. The camshaft adjuster according to claim 1, wherein the control valve is fixed in the axial direction by a non-positive fit in the driven element.
 4. The camshaft adjuster according to claim 1, wherein the driven element has an anti-rotation device for the control valve, so that an installation position defined in a peripheral direction is given.
 5. The camshaft adjuster according to claim 1, wherein the valve housing is formed in one piece with the driven element, and the driven element forms a guide surface for guiding the control piston of the control valve.
 6. The camshaft adjuster according to claim 1, wherein hydraulic medium is fed into the control valve by hydraulic medium channels formed in the camshaft.
 7. The camshaft adjuster according to claim 1, wherein the driven element has a radially projecting peg for attachment to a camshaft.
 8. The camshaft adjuster according to claim 7, wherein the peg is formed in one piece with the driven element.
 9. The camshaft adjuster according to claim 1, wherein the driven element has a part of an axial bearing and the part of the axial bearing is formed in one piece with the driven element. 